docs: def copy_cwl_files(from_dir=CWL_PATH, to_dir=None):
      """Copy cwl files to a directory where the cwl-runner can find them.
  
      Args:
          from_dir (str): Path to directory where to copy files from (default:
              the cwl directory of nlppln).
          to_dir (str): Path to directory where the files should be copied to
              (e.g., the CWL working directory).
      """
      cwl_files = glob.glob('{}{}*.cwl'.format(from_dir, os.sep))
      # if no files are found, the output directory should not be created
      if len(cwl_files) > 0:
          create_dirs(to_dir)
      for fi in cwl_files:
          fo = os.path.join(to_dir, os.path.basename(fi))
          shutil.copy2(fi, fo)
  
      return len(cwl_files)